Hurricanes can be incredibly destructive. For example, hurricane Katrina, one of the costliest and deadliest hurricanes in the history of the United States, devastated much of the north-central Gulf Coast. Katrina is believed to have caused over 1800 deaths during the storm and subsequent flooding. Damage from the storm was estimated to be over $80 billion.
A hurricane is a storm system characterized by a low pressure center, high winds in a circular pattern and numerous thunderstorms. Hurricanes are categorized based on the wind velocity of the storm. A category one hurricane has wind velocities between about 74 and 95 miles per hour while a category five hurricane, the most severe, has wind velocities in excess of 155 miles per hour. A hurricane can be conceptualized as a vertical heat engine having a primary energy source consisting of the release of the heat of condensation from water vapor condensing at high altitudes, with solar heating being the initial source for evaporation. The condensation leads to higher wind speeds, with faster winds and lower pressure causing increased surface evaporation and more condensation at higher altitudes.
The energy released during condensation at the higher altitudes drives updrafts, increasing the height of the storm clouds and increasing the rate of condensation. This positive feedback loop continues for as long as conditions are favorable. It is believed that in most instances, high humidity and water surface temperatures of at least about 80° F. are required to form and sustain a hurricane. These conditions cause the overlying atmosphere to be unstable enough to sustain convection and thunderstorms.
Hurricanes dissipate naturally when the storm moves over water having a temperature less than about 80° F. or when the hurricane moves over land. In either case, the hurricane is deprived of the humidity and warmth required to sustain the positive feedback loop that drives the storm. In the past, there have been attempts made to artificially dissipate or weaken hurricanes. For example, attempts have been made to weaken hurricanes by seeding with silver iodide. Such attempts have been generally unsuccessful and there exists a need for an artificial means of alleviating the damage caused by hurricanes by dissipating or weakening the storms.
In most large bodies of water where hurricanes occur, the temperature of the water decreases with increasing depth since most of the solar radiation (light and heat) that hits the surface is absorbed in the first few meters of water. In some locations, currents conduct cold water from the Polar Regions to warmer areas, one example being the deep western boundary current. Consequently, while the surface temperature of ocean water may be great enough to sustain a hurricane, the temperature of the water beneath the surface is typically substantially lower. Thus, there exists a need for means to exploit this temperature differential to de-energize storms such as hurricanes.